Endoscope system

ABSTRACT

First illumination light and second illumination light having different emission spectra are automatically switched so as to be emitted for a light emission period of at least one or more frames under specific light amount conditions, respectively. First image signals obtained in a case where an image is picked up using the first illumination light and second image signals obtained in a case where an image is picked up using the second illumination light are acquired. A first specific color signal for specific biological tissue among the first image signals and a second specific color signal for the specific biological tissue among the second image signals match.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of PCT International Application No.PCT/JP2019/031135 filed on 7 Aug. 2019, which claims priority under 35U.S.C. § 119(a) to Japanese Patent Application No. 2018-154122 filed on20 Aug. 2018. The above application is hereby expressly incorporated byreference, in its entirety, into the present application.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to an endoscope system that switches anddisplays a plurality of kinds of images.

2. Description of the Related Art

In recent years, an endoscope system comprising a light source device,an endoscope, and a processor device has been widely used in a medicalfield. In the endoscope system, an object to be observed is irradiatedwith illumination light from an endoscope, and the image of the objectto be observed is displayed on a monitor on the basis of RGB imagesignals that are obtained in a case where the image of the object to beobserved, which is being illuminated with the illumination light, ispicked up by an image pickup element of the endoscope.

In recent years, an object to be observed has been illuminated with aplurality of kinds of illumination light having wavelength rangesdifferent from each other according to the purpose of diagnosis. Forexample, JP2015-173737A discloses that an object to be observed isalternately illuminated with two kinds of blue narrow-band light, thatis, NB1 light having a peak wavelength of 422 nm and NB2 light having apeak wavelength in the range of 460 to 470 nm to acquire oxygensaturation in blood vessels included in the object to be observed.Further, WO2016/080130A (corresponding to US2017/0231502A1) disclosesthat an object to be observed is illuminated with light having a peak ina B1 region (first B region: 390 nm to 440 nm) and light having a peakin a B2 region (second B region: 440 nm to 490 nm) and the image of theobject to be observed is picked up by an image pickup element includingB-pixels having sensitivity to both light of the B1 region and light ofthe B2 region to obtain image information about superficial bloodvessels. Furthermore, JP2017-185258A discloses that desired tissueinformation about biological tissue is acquired as more clearinformation suitable for diagnosis using violet light having a centralwavelength of 405 nm, blue laser light having a central wavelength of445 nm, and the excitation emission of light excited and emitted by bluelaser light.

SUMMARY OF THE INVENTION

In recent years, a diagnosis focusing on information other than abackground mucous membrane, for example, blood vessels having differentdepths, glandular structures having different depths or heights, or thelike has been made in an endoscopic field. A plurality of kinds ofinformation other than the background mucous membrane need to bedisplayed in such a diagnosis so that a user can grasp the information.A method including automatically switching various kinds of light andilluminating an object with the various kinds of light, which havedifferent invasion depths to biological tissue and a plurality ofwavelengths, and switching and displaying a plurality of images obtainedfrom the illumination is considered as a method of displaying each ofthe plurality of kinds of information. For example, in order to obtaininformation about a surface layer, such as superficial blood vessels,and information about an intermediate layer, such as intermediate bloodvessels, a user illuminates an object with short-wavelength light havingan invasion depth to a surface layer and medium-wavelength light havingan invasion depth to an intermediate layer while switching theshort-wavelength light and the medium-wavelength light, and switches anddisplays a surface layer image obtained from illumination using theshort-wavelength light and an intermediate layer image obtained fromillumination using the medium-wavelength light. Since a differencebetween the surface layer image and the intermediate layer image isdisplayed in a case where such switching display is performed, the usercan grasp information about the surface layer and information about theintermediate layer.

However, in a case where a user illuminates an object with theshort-wavelength light and the medium-wavelength light while switchingthe short-wavelength light and the medium-wavelength light, the tint ofthe entire surface layer image and the tint of the entire intermediatelayer image are significantly different from each other in a case wherethe signal value of the surface layer image and the signal value of theintermediate layer image are significantly different from each other.Since a difference in the tint of the entire image is also displayed inthis case, the visibility of information about the surface layer andinformation about the intermediate layer to which a user pays attentionat the time of diagnosis deteriorates. As a method of correcting adifference in the tint of the entire image, there is a method of causingthe tint of a surface layer image and the tint of an intermediate layerimage to match using image processing, such as white balance processing.However, since a difference in a gain factor used for tint matching isgenerated in white balance processing even though the tint of a surfacelayer image and the tint of an intermediate layer image match, adifference in noise is generated between the images.

An object of the invention is to provide an endoscope system that canvisualize a difference between images while causing the tints of therespective images to match in a case where an object is illuminated witha plurality of kinds of light while the plurality of kinds of light areswitched and a plurality of images obtained from illumination using therespective kinds of light are switched and displayed.

An endoscope system according to an aspect of the invention comprises alight source unit, a light source controller, an image pickup sensor,and an image acquisition unit. The light source unit emits firstillumination light and second illumination light having an emissionspectrum different from an emission spectrum of the first illuminationlight. The light source controller automatically switches the firstillumination light and the second illumination light and emits each ofthe first illumination light and the second illumination light for alight emission period of at least one or more frames. The image pickupsensor includes specific pixels having sensitivity to the firstillumination light and the second illumination light. The imageacquisition unit acquires first image signals obtained in a case wherean image of biological tissue illuminated with the first illuminationlight is picked up by the image pickup sensor, and second image signalsobtained in a case where an image of biological tissue illuminated withthe second illumination light is picked up by the image pickup sensor.In the endoscope system according to the aspect of the invention, thefirst image signals include first specific color signals output from thespecific pixels, the second image signals include second specific colorsignals output from the specific pixels, and the light source controllercauses the first illumination light and the second illumination light tobe emitted under specific light amount conditions, so that a signalvalue of the first specific color signal for specific biological tissuecorresponding to at least specific biological tissue, which is a part ofthe biological tissue, among the first specific color signals is equalto a signal value of the second specific color signal for specificbiological tissue corresponding to at least the specific biologicaltissue among the second specific color signals.

It is preferable that a light amount condition of the first illuminationlight and a light amount condition of the second illumination light in acase where a first calculation value obtained using a light intensity ofthe first illumination light, a spectral reflectivity of the specificbiological tissue, and a spectral sensitivity of the specific pixel isequal to a second calculation value obtained using a light intensity ofthe second illumination light, the spectral reflectivity of the specificbiological tissue, and the spectral sensitivity of the specific pixelare used as the specific light amount conditions.

It is preferable that the spectral reflectivity of the specificbiological tissue is an average spectral reflectivity of a plurality ofparts obtained by averaging of spectral reflectivities of biologicaltissue of the plurality of parts. It is preferable that the plurality ofparts include a gullet, a stomach, and a large intestine. It ispreferable that the spectral reflectivity of the specific biologicaltissue is a spectral reflectivity of a background mucous membrane. It ispreferable that the spectral reflectivity of the specific biologicaltissue is an average spectral reflectivity of the entire biologicaltissue. It is preferable that the spectral reflectivity of the specificbiological tissue is any one of a spectral reflectivity of a high-oxygenportion including a specific percentage or higher of oxyhemoglobin or aspectral reflectivity of a low-oxygen portion including a specificpercentage or higher of reduced hemoglobin.

It is preferable that the endoscope system according to the aspect ofthe invention further comprises a calibration signal acquisition unitand a light amount condition-calculation unit. The calibration signalacquisition unit acquires image signals for first calibration obtainedin a case where an image of the specific biological tissue illuminatedwith different light of the first illumination light and the secondillumination light is picked up by the image pickup sensor and imagesignals for second calibration obtained in a case where an image of thespecific biological tissue illuminated with common light of the firstillumination light and the second illumination light is picked up by theimage pickup sensor. The light amount condition-calculation unitcalculates the specific light amount conditions using a specific colorsignal for first calibration output from the specific pixel among theimage signals for first calibration and a specific color signal forsecond calibration output from the specific pixel among the imagesignals for second calibration.

It is preferable that the first illumination light includes violetlight, green light, and red light, the second illumination lightincludes blue light, green light, and red light, light intensity ratiosof the green light and the red light included in the first illuminationlight are equal to light intensity ratios of the green light and the redlight included in the second illumination light, and the specific pixelis a blue pixel having sensitivity to the violet light and the bluelight.

It is preferable that the first illumination light includes violetlight, blue light, green light, and red light, a light intensity ratioof the violet light included in the first illumination light is higherthan a light intensity ratio of the blue light included in the firstillumination light, the second illumination light includes violet light,blue light, green light, and red light, a light intensity ratio of theblue light included in the second illumination light is higher than alight intensity ratio of the violet light included in the secondillumination light, light intensity ratios of the green light and thered light included in the first illumination light are equal to lightintensity ratios of the green light and the red light included in thesecond illumination light, the light intensity ratio of the violet lightincluded in the first illumination light is different from the lightintensity ratio of the violet light included in the second illuminationlight, the light intensity ratio of the blue light included in the firstillumination light is different from the light intensity ratio of theblue light included in the second illumination light, and the specificpixel is a blue pixel having sensitivity to the violet light and theblue light. It is preferable that the first illumination light includesfirst red narrow-band light and the second illumination light includessecond red narrow-band light of which a wavelength is different from awavelength of the first red narrow-band light and the specific pixel isa red pixel having sensitivity to the first red narrow-band light andthe second red narrow-band light.

It is preferable that the endoscope system further comprises a displaycontroller causing a display unit to automatically switch and display afirst observation image obtained on the basis of the first image signalsand a second observation image obtained on the basis of the second imagesignals.

According to the invention, it is possible to visualize a differencebetween images while causing the tints of the respective images to matchin a case where an object is illuminated with a plurality of kinds oflight while the plurality of kinds of light are switched and a pluralityof images obtained from illumination using the respective kinds of lightare switched and displayed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing the appearance of an endoscope systemaccording to a first embodiment.

FIG. 2 is a block diagram showing the functions of the endoscope systemaccording to the first embodiment.

FIG. 3 is a graph showing the emission spectra of violet light V, bluelight B, green light G, and red light R.

FIG. 4 is a graph showing the emission spectrum of first illuminationlight that includes violet light V, green light G, and red light R.

FIG. 5 is a graph showing the emission spectrum of second illuminationlight that includes blue light B, green light G, and red light R.

FIG. 6 is a diagram illustrating the light emission period of the firstillumination light and the light emission period of the secondillumination light.

FIG. 7 is a diagram illustrating a light emission period-setting menu.

FIG. 8 shows the spectral transmittance of a B-filter, a G-filter, andan R-filter provided in an image pickup sensor.

FIG. 9 is an image diagram showing a first special observation image.

FIG. 10 is a diagram illustrating a violet light image and a green-redlight image that are obtained in a case where an object is illuminatedwith the first illumination light.

FIG. 11 is an image diagram showing a second special observation image.

FIG. 12 is a diagram illustrating a blue light image and a green-redlight image that are obtained in a case where an object is illuminatedwith the second illumination light.

FIG. 13 is a diagram illustrating the switching display of a firstspecial observation image and a second special observation image thatare color images.

FIG. 14 is a diagram illustrating the switching display of a firstspecial observation image and a second special observation image ofwhich the tints of background mucous membranes match.

FIG. 15 is a diagram illustrating the switching display of a firstspecial observation image and a second special observation image ofwhich the tints of background mucous membranes are different from eachother.

FIG. 16 is a diagram illustrating the switching display of a firstspecial observation image and a second special observation image ofwhich the tints of background mucous membranes are different from eachother.

FIG. 17 is a diagram illustrating a method of calculating a firstcalculation value.

FIG. 18 is a diagram illustrating a method of calculating a secondcalculation value.

FIG. 19 is a diagram illustrating the average spectral reflectivity of aplurality of parts.

FIG. 20 is a diagram illustrating the spectral reflectivity of abackground mucous membrane.

FIG. 21 is a diagram illustrating the average spectral reflectivity ofthe entire biological tissue.

FIG. 22 is a graph showing the spectral reflectivities of a high-oxygenportion and a low-oxygen portion.

FIG. 23 is a diagram illustrating the switching display of a firstspecial observation image and a second special observation image ofwhich the tints of high-oxygen portions match.

FIG. 24 is a diagram illustrating the switching display of a firstspecial observation image and a second special observation image thatare monochrome images.

FIG. 25 is a diagram illustrating a display period-setting menu.

FIG. 26 is a graph showing the emission spectrum of first illuminationlight that includes violet light V, blue light B, green light G, and redlight R.

FIG. 27 is a graph showing the emission spectrum of second illuminationlight that includes violet light V, blue light B, green light G, and redlight R.

FIG. 28 is a graph showing the emission spectrum of first illuminationlight including first red narrow-band light.

FIG. 29 is a graph showing the emission spectrum of first illuminationlight including second red narrow-band light.

FIG. 30 is a block diagram showing the functions of an endoscope systemaccording to another aspect of the first embodiment.

FIG. 31 is a block diagram showing the functions of an endoscope systemaccording to a second embodiment.

FIG. 32 is a diagram illustrating image signals for violet lightcalibration.

FIG. 33 is a diagram illustrating image signals for blue lightcalibration.

FIG. 34 is a diagram illustrating image signals for green/red lightcalibration.

DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment

As shown in FIG. 1, an endoscope system 10 according to a firstembodiment includes an endoscope 12, a light source device 14, aprocessor device 16, a monitor 18 (display unit), and a user interface19. The endoscope 12 is optically connected to the light source device14, and is electrically connected to the processor device 16. Theendoscope 12 includes an insertion part 12 a that is to be inserted intoan object to be examined, an operation part 12 b that is provided at theproximal end portion of the insertion part 12 a, and a bendable part 12c and a distal end part 12 d that are provided on the distal end side ofthe insertion part 12 a. In a case where angle knobs 12 e of theoperation part 12 b are operated, the bendable part 12 c is operated tobe bent. As the bendable part 12 c is operated to be bent, the distalend part 12 d faces in a desired direction. The user interface 19includes a mouse and the like in addition to a keyboard shown in FIG. 1.

Further, the operation part 12 b is provided with a mode changeover SW13 a and a static image-acquisition instruction unit 13 b in addition tothe angle knobs 12 e. The mode changeover SW 13 a is used for anoperation for switching a normal observation mode, a first specialobservation mode, a second special observation mode, and amulti-observation mode. The normal observation mode is a mode where anormal image is displayed on the monitor 18. The first specialobservation mode is a mode where a first special observation image inwhich surface layer information, such as superficial blood vessels, areemphasized is displayed on the monitor 18. The second specialobservation mode is a mode where a second special observation image inwhich intermediate layer information, such as intermediate bloodvessels, are emphasized is displayed on the monitor 18. Themulti-observation mode is a mode where the first special observationimage (first observation image) and the second special observation image(second observation image) are automatically switched and displayed onthe monitor 18. A foot switch may be used as a mode switching unit,which is used to switch a mode, other than the mode changeover SW 13 a.

The processor device 16 is electrically connected to the monitor 18 andthe user interface 19. The monitor 18 outputs and displays imageinformation and the like. The user interface 19 functions as a userinterface (UI) that receives an input operation, such as functionsettings. An external recording unit (not shown), which records imageinformation and the like, may be connected to the processor device 16.

As shown in FIG. 2, the light source device 14 includes a light sourceunit 20, a light source controller 21, and an optical path-combinationunit 23. The light source unit 20 includes a violet light emitting diode(V-LED) 20 a, a blue light emitting diode (B-LED) 20 b, a green lightemitting diode (G-LED) 20 c, and a red light emitting diode (R-LED) 20d. The light source controller 21 controls the drive of the LEDs 20 a to20 d. The optical path-combination unit 23 combines the optical paths offour kinds of color light that are emitted from the four color LEDs 20 ato 20 d. The inside of an object to be examined is irradiated with thepieces of light, which are combined by the optical path-combination unit23, through a light guide 41 inserted into the insertion part 12 a andan illumination lens 45. A laser diode (LD) may be used instead of theLED.

As shown in FIG. 3, the V-LED 20 a generates violet light V of which thecentral wavelength is in the range of 405±10 nm and the wavelength rangeis in the range of 380 to 420 nm. The B-LED 20 b generates blue light Bof which the central wavelength is in the range of 460±10 nm and thewavelength range is in the range of 420 to 500 nm. The G-LED 20 cgenerates green light G of which the wavelength range is in the range of480 to 600 nm. The R-LED 20 d generates red light R of which the centralwavelength is in the range of 620 to 630 nm and the wavelength range isin the range of 600 to 650 nm.

The light source controller 21 controls the V-LED 20 a, the B-LED 20 b,the G-LED 20 c, and the R-LED 20 d. Further, the light source controller21 controls the respective LEDs 20 a to 20 d so that normal light ofwhich the light intensity ratios of violet light V, blue light B, greenlight G, and red light R are Vc:Bc:Gc:Rc is emitted in the normalobservation mode.

Furthermore, the light source controller 21 controls the respective LEDs20 a to 20 d so that first illumination light of which the lightintensity ratios of violet light V, blue light B, green light G, and redlight R are Vs1:Bs1:Gs1:Rs1 is emitted in the first special observationmode. The light intensity ratios Vs1:Bs1:Gs1:Rs1 correspond to the lightamount condition of the first illumination light. It is preferable thatthe first illumination light can emphasize superficial blood vessels andaccurately reproduce the color of a background mucous membrane. For thispurpose, it is preferable that, for example, Bs1 is set to “0” and Vs1,Gs1, and Rs1 are set to be larger than “0” as shown in FIG. 4. Since thefirst illumination light in this case includes violet light, greenlight, and red light, the first illumination light can emphasize theabove-mentioned superficial blood vessels, accurately reproduce thecolor of a background mucous membrane, and also emphasize variousstructures, such as glandular structures and unevenness.

In this specification, the light intensity ratios include a case wherethe ratio of at least one semiconductor light source is 0 (zero).Accordingly, the light intensity ratios include a case where any one ortwo or more of the respective semiconductor light sources are not turnedon. For example, even though only one semiconductor light source isturned on and the other three semiconductor light sources are not turnedon as in a case where the light intensity ratios of violet light V, bluelight B, green light G, and red light R are 1:0:0:0, it is regarded thatthe light source unit 20 has light intensity ratios.

Further, the light source controller 21 controls the respective LEDs 20a to 20 d so that second illumination light of which the light intensityratios of violet light V, blue light B, green light G, and red light Rare Vs2:Bs2:Gs2:Rs2 is emitted in the second special observation mode.The light intensity ratios Vs2:Bs2:Gs2:Rs2 correspond to the lightamount condition of the second illumination light. It is preferable thatthe second illumination light can emphasize intermediate blood vesselsand accurately reproduce the color of a background mucous membrane. Forthis purpose, it is preferable that, for example, Vs2 is set to “0” andBs2, Gs2, and Rs2 are set to be larger than “0” as shown in FIG. 5.Since the second illumination light in this case includes blue light,green light, and red light, the second illumination light can emphasizeintermediate blood vessels and accurately reproduce the color of abackground mucous membrane.

In a case where a mode is set to the multi-observation mode, the lightsource controller 21 performs control to emit each of the firstillumination light and the second illumination light for a lightemission period of one or more frames and to automatically switch andemit the first illumination light and the second illumination light.Further, the light source controller 21 controls the light source unit20 so that the light amount condition of the first illumination lightand the light amount condition of the second illumination light are setto specific light amount conditions and light is emitted. Since thefirst illumination light and the second illumination light are emittedunder the specific light amount conditions, the signal value of a firstblue color signal for specific biological tissue corresponding to atleast specific biological tissue, which is a part of biological tissue,among first blue color signals (first specific color signals) includedin the first special observation image is equal to the signal value of asecond blue color signal for specific biological tissue corresponding toat least the specific biological tissue among second blue color signals(second specific color signals) included in the second specialobservation image. Under the specific light amount conditions, the lightintensity ratio (Gs1:Rs1) of green light G and red light R included inthe first illumination light and the light intensity ratio (Gs2:Rs2) ofgreen light G and red light R included in the second illumination lightare set to be equal to each other.

Accordingly, the tints of the background mucous membranes of the firstand second special observation images match. Here, a case where thesignal value of the first blue color signal for specific biologicaltissue and the signal value of the second blue color signal for specificbiological tissue are equal to each other also includes a case where adifference between the signal value of the first blue color signal forspecific biological tissue and the signal value of the second blue colorsignal for specific biological tissue is in a certain allowable rangeeven though the signal value of the first blue color signal for specificbiological tissue and the signal value of the second blue color signalfor specific biological tissue are different from each other, inaddition to a case where the signal values are completely equal to eachother. The details of a method of setting the specific light amountconditions will be described later. The background mucous membrane meansa region of an object to be observed not including regions that are tobe recognized or subjected to image pickup as structures, such as bloodvessels or glandular structures.

Moreover, the light source controller 21 controls the amount ofillumination light to be emitted from each of the LEDs 20 a to 20 d onthe basis of lightness information sent from a lightness informationcalculation unit 54 of the processor device 16. Further, for example, ina case where the light source controller 21 sets the light emissionperiod of the first illumination light to two frames and sets the lightemission period of the second illumination light to three frames, thesecond illumination light continues to be emitted for three frames afterthe first illumination light continues to be emitted for two frames asshown in FIG. 6.

“Frame” means a unit used to control an image pickup sensor 48 thatpicks up the image of an object to be observed. For example, “one frame”means a period including at least an exposure period where the imagepickup sensor 48 is exposed to light emitted from an object to beobserved and a read-out period where image signals are read out. In thisembodiment, the light emission period is determined so as to correspondto “frame” that is a unit of image pickup.

The light emission period of the first illumination light and the lightemission period of the second illumination light can be appropriatelychanged by a light emission period-setting unit 24 that is connected tothe light source controller 21. In a case where an operation forchanging a light emission period is received by the operation of theuser interface 19, the light emission period-setting unit 24 displays alight emission period-setting menu shown in FIG. 7 on the monitor 18.The light emission period of the first illumination light can be changedbetween, for example, two frames and ten frames. Each light emissionperiod is assigned to a slide bar 26 a.

In a case where the light emission period of the first illuminationlight is to be changed, a user operates the user interface 19 toposition a slider 27 a at a position on the slide bar 26 a thatrepresents a light emission period to which the user wants to change alight emission period. Accordingly, the light emission period of thefirst illumination light is changed. Even in the case of the lightemission period of the second illumination light, a user operates theuser interface 19 to position a slider 27 b at a position on a slide bar26 b (to which a light emission period in the range of, for example, twoframes to ten frames is assigned) that represents a light emissionperiod to which the user wants to change a light emission period.Accordingly, the light emission period of the second illumination lightis changed.

As shown in FIG. 2, the light guide 41 is built in the endoscope 12 anda universal cord (a cord connecting the endoscope 12 to the light sourcedevice 14 and the processor device 16), and transmits the pieces oflight, which are combined by the optical path-combination unit 23, tothe distal end part 12 d of the endoscope 12. A multimode fiber can beused as the light guide 41. For example, a thin fiber cable of which atotal diameter of a core diameter of 105 μm, a cladding diameter of 125μm, and a protective layer forming a covering is in the range of φ0.3 to0.5 mm can be used.

The distal end part 12 d of the endoscope 12 is provided with anillumination optical system 30 a and an image pickup optical system 30b. The illumination optical system 30 a includes an illumination lens45, and an object to be observed is irradiated with light transmittedfrom the light guide 41 through the illumination lens 45. The imagepickup optical system 30 b includes an objective lens 46 and an imagepickup sensor 48. Light reflected from the object to be observed isincident on the image pickup sensor 48 through the objective lens 46.Accordingly, the reflected image of the object to be observed is formedon the image pickup sensor 48.

The image pickup sensor 48 is a color image pickup sensor, and picks upthe reflected image of an object to be examined and outputs imagesignals. It is preferable that the image pickup sensor 48 is a chargecoupled device (CCD) image pickup sensor, a complementary metal-oxidesemiconductor (CMOS) image pickup sensor, or the like. The image pickupsensor 48 used in the invention is a color image pickup sensor used toobtain RGB image signals corresponding to three colors of R (red), G(green), and B (blue), that is, a so-called RGB image pickup sensor thatcomprises R-pixels (specific pixels) provided with R-filters, G-pixelsprovided with G-filters, and B-pixels (specific pixels) provided withB-filters.

As shown in FIG. 8, the B-filter 48 b transmits light of a violet-lightwavelength range, light of a blue-light wavelength range, andshort-wavelength light of light of a green-light wavelength range. TheG-filter 48 g transmits light of a green-light wavelength range,long-wavelength light of light of a blue-light wavelength range, andshort-wavelength light of light of a red-light wavelength range. TheR-filter 48 r transmits light of a red-light wavelength range andshort-wavelength light of light of a green-light wavelength range.Accordingly, in the image pickup sensor 48, the B-pixel has sensitivityto violet light V, blue light B, and green light G, the G-pixel hassensitivity to blue light B, green light G, and red light R, and theR-pixel has sensitivity to green light G and red light R.

The image pickup sensor 48 may be a so-called complementary color imagepickup sensor, which comprises complementary color filters correspondingto C (cyan), M (magenta), Y (yellow), and G (green), instead of an RGBcolor image pickup sensor. In a case where a complementary color imagepickup sensor is used, image signals corresponding to four colors of C,M, Y, and G are output. Accordingly, the image signals corresponding tofour colors of C, M, Y, and G need to be converted into image signalscorresponding to three colors of R, G, and B by complementarycolor-primary color conversion. Further, the image pickup sensor 48 maybe a monochrome image pickup sensor that includes no color filter. Inthis case, since the light source controller 21 causes blue light B,green light G, and red light R to be emitted in a time-sharing manner,demosaicing needs to be added to processing for image pickup signals.

As shown in FIG. 2, the image signals output from the image pickupsensor 48 are transmitted to a CDS/AGC circuit 50. The CDS/AGC circuit50 performs correlated double sampling (CDS) or auto gain control (AGC)on the image signals that are analog signals. The image signals, whichhave been transmitted through the CDS/AGC circuit 50, are converted intodigital image signals by an analog/digital converter (A/D converter) 52.The digital image signals, which have been subjected to A/D conversion,are input to the processor device 16.

The processor device 16 comprises an image acquisition unit 53, alightness information calculation unit 54, a digital signal processor(DSP) 56, a noise removing unit 58, a signal switching unit 60, a normalobservation image processing unit 62, a first special observation imageprocessing unit 63, a second special observation image processing unit64, a display controller 66, a static image storage unit 67, and astatic image-storage controller 68.

The image acquisition unit 53 acquires an observation image that isobtained in a case where the image of the object to be observed ispicked up in the endoscope 12. Specifically, digital color image signalsobtained from the endoscope 12 are input to the image acquisition unit53 as an observation image. The color image signals are formed of redcolor signals output from the R-pixels of the image pickup sensor 48,green color signals output from the G-pixels of the image pickup sensor48, and blue color signals output from the B-pixels of the image pickupsensor 48. The lightness information calculation unit 54 calculateslightness information, which represents the lightness of the object tobe observed, on the basis of the image signals input from the imageacquisition unit 53. The calculated lightness information is sent to thelight source controller 21 and is used for the control of the amount ofillumination light to be emitted.

The DSP 56 performs various kinds of signal processing, such as defectcorrection processing, offset processing, gain correction processing,linear matrix processing, gamma conversion processing, and demosaicingprocessing, on the received image signals. Signals of defective pixelsof the image pickup sensor 48 are corrected in the defect correctionprocessing. Dark current components are removed from the image signalshaving been subjected to the defect correction processing in the offsetprocessing, so that an accurate zero level is set. The image signalshaving been subjected to the offset processing are multiplied by aspecific gain in the gain correction processing, so that signal levelsare adjusted. The linear matrix processing for improving colorreproducibility is performed on the image signals having been subjectedto the gain correction processing. After that, lightness or a saturationis adjusted by the gamma conversion processing. The demosaicingprocessing (also referred to as equalization processing or demosaicing)is performed on the image signals having been subjected to the linearmatrix processing, so that signals of colors deficient in each pixel aregenerated by interpolation. All the pixels are made to have the signalsof the respective colors by this demosaicing processing.

The noise removing unit 58 performs noise removal processing (forexample, a moving-average method, median filtering, or the like) on theimage signals, which have been subjected to gamma correction and thelike by the DSP 56, to remove noise from the image signals. The imagesignals from which noise has been removed are transmitted to the signalswitching unit 60.

In a case where a mode is set to the normal observation mode by the modechangeover SW 13 a, the signal switching unit 60 transmits image signalsfor normal light, which are obtained through the illumination of normallight and image pickup, to the normal observation image processing unit62. Further, in a case where a mode is set to the first specialobservation mode, the signal switching unit 60 transmits first imagesignals, which are obtained through the illumination of the firstillumination light and image pickup, to the first special observationimage processing unit 63. The first image signals include first redcolor signals that are output from the R-pixels of the image pickupsensor, first green color signals that are output from the G-pixels ofthe image pickup sensor 48, and first blue color signals that are outputfrom the B-pixels of the image pickup sensor 48. Furthermore, in a casewhere a mode is set to the second special observation mode, the signalswitching unit 60 transmits second image signals, which are obtainedthrough the illumination of the second illumination light and imagepickup, to the second special observation image processing unit 64. Thesecond image signals include second red color signals that are outputfrom the R-pixels of the image pickup sensor, second green color signalsthat are output from the G-pixels of the image pickup sensor 48, andsecond blue color signals that are output from the B-pixels of the imagepickup sensor 48. Moreover, in a case where a mode is set to themulti-observation mode, first image signals obtained through theillumination of the first illumination light and image pickup aretransmitted to the first special observation image processing unit 63and second image signals obtained through the illumination of the secondillumination light and image pickup are transmitted to the secondspecial observation image processing unit 64.

The normal observation image processing unit 62 performs imageprocessing for a normal image on the RGB image signals that are obtainedin the normal observation mode. The image processing for a normal imageincludes structure emphasis processing for a normal image and the like.The normal observation image processing unit 62 includes parameters fora normal image, which are to be multiplied by the RGB image signals, toperform the image processing for a normal image. The RGB image signalshaving been subjected to the image processing for a normal image areinput to the display controller 66 from the normal observation imageprocessing unit 62 as a normal image.

The first special observation image processing unit 63 generates thefirst special observation image having been subjected to imageprocessing (image processing for a first special observation image),such as saturation emphasis processing, hue emphasis processing, andstructure emphasis processing, on the basis of the first image signals.In the first special observation image, many superficial blood vesselsare included and the color of the background mucous membrane is alsoaccurately reproduced. The first special observation image processingunit 63 includes parameters for a first special observation image, whichare to be multiplied by the first image signals, to perform the imageprocessing for a first special observation image. The first specialobservation image processing unit 63 does not perform superficial bloodvessel emphasis processing for emphasizing superficial blood vessels,but may perform the superficial blood vessel emphasis processingdepending on the situation of a processing load.

A first special observation image in which a background mucous membraneBM of an object to be observed and superficial blood vessels VS1 areshown is displayed as the first special observation image as shown inFIG. 9. The first special observation image is obtained on the basis ofthe first illumination light that includes violet light, green light,and red light. In a case where an object to be observed is illuminatedwith the first illumination light, violet light V of the firstillumination light reaches a surface layer where the superficial bloodvessels VS1 are distributed as shown in FIG. 10. Accordingly, the imageof the superficial blood vessels VS1 is included in a violet light imageVP that is obtained on the basis of the reflected light of the violetlight V. Further, green light G and red light R of the firstillumination light reach the background mucous membrane BM that isdistributed at a position deeper than the superficial blood vessels VS1and intermediate blood vessels VS2 (blood vessels present at positionsdeeper than the superficial blood vessels VS1). Accordingly, the imageof the background mucous membrane BM is included in a green-red lightimage GRP that is obtained on the basis of the reflected light of thegreen light G and the red light R. Since the first special observationimage is an image in which the violet light image VP and the green-redlight image GRP are combined with each other as described above, theimages of the background mucous membrane BM and the superficial bloodvessels VS1 are displayed.

The second special observation image processing unit 64 generates thesecond special observation image having been subjected to imageprocessing (image processing for a second special observation image),such as saturation emphasis processing, hue emphasis processing, andstructure emphasis processing, on the basis of the second image signals.In the second special observation image, many intermediate blood vesselsare included and the color of the background mucous membrane is alsoaccurately reproduced. The second special observation image processingunit 64 includes parameters for a second special observation image,which are to be multiplied by the second image signals, to perform theimage processing for a second special observation image. The secondspecial observation image processing unit 64 does not performintermediate blood vessel emphasis processing for emphasizingintermediate blood vessels, but may perform the intermediate bloodvessel emphasis processing depending on the situation of a processingload.

A second special observation image in which a background mucous membraneBM of an object to be observed and intermediate blood vessels VS2 areshown is displayed as the second special observation image as shown inFIG. 11. The second special observation image is obtained on the basisof the second illumination light that includes blue light, green light,and red light. In a case where the object to be observed is illuminatedwith the second illumination light, blue light B of the secondillumination light reaches an intermediate layer where the intermediateblood vessels VS2 are distributed as shown in FIG. 12. Accordingly, theimage of the intermediate blood vessels VS2 is included in a blue lightimage BP that is obtained on the basis of the reflected light of theblue light B. Further, green light G and red light R of the secondillumination light reach the background mucous membrane BM that isdistributed at a position deeper than the superficial blood vessels VS1and the intermediate blood vessels VS2 (blood vessels present atpositions deeper than the superficial blood vessels VS1). Accordingly,the image of the background mucous membrane BM is included in agreen-red light image GRP that is obtained on the basis of the reflectedlight of the green light G and the red light R. Since the second specialobservation image is an image in which the blue light image BP and thegreen-red light image GRP are combined with each other as describedabove, the images of the background mucous membrane BM and theintermediate blood vessels VS2 are displayed.

The display controller 66 performs control to display the normal image,the first special observation image, or the second special observationimage, which are input from the normal observation image processing unit62, the first special observation image processing unit 63, or thesecond special observation image processing unit 64, as images that canbe displayed on the monitor 18. An image corresponding to eachobservation mode is displayed by the control of the display controller66. In the normal observation mode, the normal image is displayed on themonitor 18. Further, the first special observation image (see FIG. 9) isdisplayed on the monitor 18 in the first special observation mode.Furthermore, the second special observation image (see FIG. 11) isdisplayed on the monitor 18 in the second special observation mode.

Moreover, in the multi-observation mode, the first special observationimage and the second special observation image, which are color images,are switched and displayed on the monitor 18 according to the lightemission period of the first illumination light and the light emissionperiod of the second illumination light. That is, in a case where thelight emission period of the first illumination light is two frames andthe light emission period of the second illumination light is threeframes, the first special observation image continues to be displayedfor two frames and the second special observation image continues to bedisplayed for three frames.

As described above, two kinds of the first and second specialobservation images can be automatically switched and displayed in themulti-observation mode without the operation of the mode changeover SW13 a that is performed by a user. Since the first and second specialobservation images are automatically switched and displayed as describedabove, the same object to be observed is displayed in the first andsecond special observation images as long as the object to be observedis not moved or the distal end part 12 d of the endoscope 12 is notmoved. However, since the spectral information of the first specialobservation image and the spectral information of the second specialobservation image are different from each other even in the case of thesame object to be observed, the object to be observed looks differentdepending on a difference in spectral information. That is, thevisibility of the superficial blood vessels is high in the first specialobservation image, but the visibility of the intermediate blood vesselsis high in the second special observation image. Accordingly, since thefirst and second special observation images are switched and displayed,the visibility of a plurality of blood vessels having different depthscan be improved.

Further, since the light amount condition of the first illuminationlight and the light amount condition of the second illumination lightused in the multi-observation mode are set to the specific light amountconditions and light is emitted, the tint of a background mucousmembrane BM of a first special observation image SP1 and the tint of abackground mucous membrane BM of a second special observation image SP2match as shown in FIG. 14. The reason for this is that the signal valueof a first blue color signal for specific biological tissue among firstblue color signals included in the first special observation image isequal to the signal value of a second blue color signal for specificbiological tissue among second blue color signals included in the secondspecial observation image. Since the first and second specialobservation images SP1 and SP2 of which the background mucous membranesBM match are switched and displayed as described above, only differencesbetween superficial components and intermediate components are changed,that is, the superficial blood vessels and the intermediate bloodvessels are switched and displayed. Accordingly, the superficialcomponents and the intermediate components can be visually recognized.

On the other hand, in a case where the signal value of the first bluecolor signal is larger than the signal value of the second blue colorsignal, the background mucous membrane BM of the first specialobservation image SP1 has a blue color but the background mucousmembrane BM of the second special observation image SP2 has a yellowcolor as shown in FIG. 15. For this reason, the tint of the backgroundmucous membrane BM of the first special observation image SP1 and thetint of the background mucous membrane BM of the second specialobservation image SP2 are different from each other. Accordingly, it isnot possible to visually recognize which portions are the superficialblood vessels VS1 or the intermediate blood vessels VS2. In contrast, ina case where the signal value of the first blue color signal is smallerthan the signal value of the second blue color signal, the backgroundmucous membrane BM of the first special observation image SP1 has ayellow color but the background mucous membrane BM of the second specialobservation image SP2 has a blue color as shown in FIG. 16. Even in thiscase, the tint of the background mucous membrane BM of the first specialobservation image SP1 and the tint of the background mucous membrane BMof the second special observation image SP2 are different from eachother. Accordingly, it is not possible to visually recognize whichportions are the superficial blood vessels VS1 or the intermediate bloodvessels VS2.

The static image-storage controller 68 performs control to store animage, which is obtained according to the instruction of the staticimage-acquisition instruction unit 13 b at the timing of a staticimage-acquisition instruction, in the static image storage unit 67 as astatic image. In the normal observation mode, the static image-storagecontroller 68 stores a normal image, which is obtained at the timing ofthe static image-acquisition instruction, in the static image storageunit 67 as a static image. In the first special observation mode, thestatic image-storage controller 68 stores a first special observationimage, which is obtained at the timing of the static image-acquisitioninstruction, in the static image storage unit 67 as a static image. Inthe second special observation mode, the static image-storage controller68 stores a second special observation image, which is obtained at thetiming of the static image-acquisition instruction, in the static imagestorage unit 67 as a static image. Further, in the multi-observationmode, the static image-storage controller 68 stores a set of observationimages for display, which is formed of the first special observationimage and the second special observation image obtained at the timing ofthe static image-acquisition instruction, in the static image storageunit 67.

Next, the details of the specific light amount conditions will bedescribed. The specific light amount conditions are the light amountcondition of the first illumination light and the light amount conditionof the second illumination light determined so that the signal value ofthe first blue color signal for specific biological tissue and thesignal value of the second blue color signal for specific biologicaltissue are equal to each other. In the first embodiment, on the premisethat the spectral reflectivity S(λ) of specific biological tissue isalready known, a first calculation value B1 is used as a valuecorresponding to the signal value of a first blue color signal used tocalculate a specific light amount condition and a second calculationvalue B2 is used as a value corresponding to the signal value of asecond blue color signal used to calculate a specific light amountcondition.

As shown in FIG. 17, the first calculation value B1 is obtained fromEquation 1) on the basis of the light intensity E1(λ) of the firstillumination light, the spectral reflectivity S(λ) of specificbiological tissue, and the spectral sensitivity b(λ) of the B-pixel ofthe image pickup sensor 48 (sensitivity is expressed as “transmittance(%)” in FIG. 17).

B1=∫E1(λ)×S(λ)×b(λ)dλ  Equation 1)

As shown in FIG. 18, the second calculation value is obtained fromEquation 2) on the basis of the light intensity E2(λ) of the secondillumination light, the spectral reflectivity S(λ) of specificbiological tissue, and the spectral sensitivity b(λ) of the B-pixel ofthe image pickup sensor 48 (sensitivity is expressed as “transmittance(%)” in FIG. 18).

B2=∫E2(λ)×S(λ)×b(λ)dλ  Equation 2)

The light intensity E1(λ) of the first illumination light and the lightintensity E2(λ) of the second illumination light are determined so thatthe first calculation value B1 obtained from Equation 1) and the secondcalculation value B2 obtained from Equation 2) are equal to each other.Here, the first calculation value B1 and the second calculation value B2are made to be equal to each other through the adjustment of the lightintensity (Vs1) of violet light V and the light intensity (Bs2) of bluelight B in a state where the light intensities (Gs1 and Rs1) of greenlight G and red light R included in the first illumination light areequal to the light intensities (Gs2 and Rs2) of green light G and redlight R included in the second illumination light. The light intensityE1(λ) of the first illumination light and the light intensity E2(λ) ofthe second illumination light, which are obtained in a case where thefirst calculation value B1 and the second calculation value B2 are madeto be equal to each other, are set as the specific light amountconditions. A case where the first calculation value B1 and the secondcalculation value B2 are equal to each other includes a case where adifference between the first calculation value B1 and the secondcalculation value B2 is in a certain allowable range even though thefirst calculation value B1 and the second calculation value B2 aredifferent from each other, in addition to a case where the firstcalculation value B1 and the second calculation value are completelyequal to each other.

For example, the spectral reflectivities of biological tissue of aplurality of parts may be used as the spectral reflectivity of specificbiological tissue. Specifically, as shown in FIG. 19, the averagespectral reflectivity of a plurality of parts, which is obtained by theaveraging of the spectral reflectivity of the gullet, the spectralreflectivity of the stomach, and the spectral reflectivity of the largeintestine, is defined as the spectral reflectivity of specificbiological tissue. It is preferable that the reflectivity (alreadyknown) of a standard human body is used for each of the spectralreflectivity of the gullet, the spectral reflectivity of the stomach,and the spectral reflectivity of the large intestine.

Further, for example, the spectral reflectivity (already known) of thebackground mucous membrane BM, which is a part of biological tissue, maybe used as the spectral reflectivity of specific biological tissue asshown in FIG. 20. The spectral reflectivity of the background mucousmembrane BM may be the spectral reflectivity of a background mucousmembrane that is included in any one of parts, such as the gullet, thestomach, and the large intestine; or may be an average value of thespectral reflectivities of the background mucous membranes included inthe respective parts.

Furthermore, for example, the average spectral reflectivity of theentire biological tissue including the superficial blood vessels VS1,the intermediate blood vessels VS2, and the background mucous membraneBM may be used as the spectral reflectivity of specific biologicaltissue as shown in FIG. 21. Specifically, the average value of thespectral reflectivity of the superficial blood vessels VS1, the spectralreflectivity of the intermediate blood vessels VS2, and the spectralreflectivity of the background mucous membrane BM may be used as theaverage spectral reflectivity of the entire biological tissue.

Further, any one of the spectral reflectivity of a high-oxygen portionof biological tissue that includes a specific percentage or higher ofoxyhemoglobin in blood vessels, or the spectral reflectivity of alow-oxygen portion of biological tissue that includes a specificpercentage or higher of reduced hemoglobin in blood vessels may be usedas the spectral reflectivity of specific biological tissue. As shown inFIG. 22, the spectral reflectivity of the high-oxygen portion is shownby a graph 70 and the spectral reflectivity of the low-oxygen portion isshown by a graph 71. For example, in a case where the spectralreflectivity of the high-oxygen portion is used as the spectralreflectivity of specific biological tissue to determine a specific lightamount condition, the tint of a high-oxygen portion 74 of the firstspecial observation image SP1 and the tint of a high-oxygen portion 76of the second special observation image SP2 match as shown in FIG. 23.On the other hand, the tint of a low-oxygen portion 78 of the firstspecial observation image SP1 and the tint of a low-oxygen portion 80 ofthe second special observation image are different from each other.

Accordingly, in a case where the first special observation image SP1 andthe second special observation image SP2 are switched and displayed, thelow-oxygen portion 78 of the first special observation image SP1 and thelow-oxygen portion 80 of the second special observation image aredisplayed so as to flicker. Since the low-oxygen portions 78 and 80 aredisplayed so as to flicker as described above, the low-oxygen portions78 and 80 can be visually recognized even though the low-oxygen portions78 and 80 have low contrast in the images. In a case where the spectralreflectivity of the low-oxygen portion is used as the spectralreflectivity of specific biological tissue to determine a specific lightamount condition, the tints of the low-oxygen portions of the first andsecond special observation images match and the high-oxygen portions aredisplayed so as to flicker by the switching of the first and secondspecial observation images.

The first and second special observation images are displayed in themulti-observation mode as color images, but the first and second specialobservation images may be displayed as monochrome images instead ofcolor images as shown in FIG. 24. In a case where the first and secondspecial observation images as monochrome images are switched anddisplayed in this way, a change in color hardly occurs at portions otherthan blood vessels, such as superficial blood vessels and intermediateblood vessels. Accordingly, a user can pay attention to and observeblood vessels having different depths, such as superficial blood vesselsand intermediate blood vessels, without a sense of incongruity in thecase of the switching of the first and second special observationimages.

The display period of the first special observation image and thedisplay period of the second special observation image can beappropriately changed by a display period-setting unit 66 a that isprovided in the display controller 66 (see FIG. 2). In a case where anoperation for changing a display period is received by the operation ofthe user interface 19, the display period-setting unit 66 a displays adisplay period-setting menu shown in FIG. 25 on the monitor 18. Thedisplay period of the first special observation image can be changedbetween, for example, two frames and ten frames. Each display period isassigned to a slide bar 84 a.

In a case where the display period of the first special observationimage is to be changed, a user operates the user interface 19 toposition a slider 86 a at a position on the slide bar 84 a thatrepresents a display period to which the user wants to change a displayperiod. Accordingly, the display period of the first special observationimage is changed. Even in the case of the display period of the secondspecial observation image, a user operates the user interface 19 toposition a slider 86 b at a position on a slide bar 84 b (to which adisplay period in the range of, for example, two frames to ten frames isassigned) that represents a display period to which the user wants tochange a display period. Accordingly, the display period of the secondspecial observation image is changed.

In a case where the light emission period of the first illuminationlight is shorter than the display period of the first specialobservation image, it is preferable that a first special observationimage corresponding to the display period is generated by complementaryprocessing or the like so as to be displayed for the display period ofthe first special observation image. In contrast, in a case where thelight emission period of the second illumination light is longer thanthe display period of the first special observation image, the firstspecial observation image may not be used for display according to thedisplay period of the first special observation image. Further, it ispreferable that the display periods of the first and second specialobservation images are set to at least two or more frames. Since theimages are quickly switched in a case where the display periods of thefirst and second special observation images are set to one frame, thereis a concern that a user cannot recognize a difference between the firstand second special observation images.

The first illumination light includes violet light V, green light G, andred light R in the embodiment. However, as shown in FIG. 26, blue lightB may be added to the first illumination light so that the firstillumination light includes violet light V, blue light B, green light G,and red light R. In this case, the light intensity of violet light V isset to be higher than the light intensity of blue light B. For example,it is preferable that a ratio between the light intensity Vs1 of violetlight V and the light intensity Bs1 of blue light B is set to “9:1”.Further, the second illumination light includes blue light B, greenlight G, and red light R. However, as shown in FIG. 27, violet light Vmay be added to the second illumination light so that the secondillumination light includes violet light V, blue light B, green light G,and red light R. In this case, the light intensity of blue light B isset to be higher than the light intensity of violet light V. Forexample, it is preferable that a ratio between the light intensity Vs2of violet light V and the light intensity Bs2 of blue light B is set to“1:9”. In a case where each of the first illumination light and thesecond illumination light includes violet light V, blue light B, greenlight G, and red light R as described above, it is preferable that theintensity ratio of violet light included in the first illumination lightand the intensity ratio of violet light included in the secondillumination light are set to be different from each other and theintensity ratio of blue light included in the first illumination lightand the intensity ratio of blue light included in the secondillumination light are set to be different from each other in a statewhere the light intensity ratios of green light and red light includedin the first illumination light are equal to the light intensity ratiosof green light and red light included in the second illumination light.

Further, first red narrow-band light NR1 of which the central wavelengthor the peak wavelength is in the range of 560 to 580 nm as shown in FIG.28 may be included in the first illumination light instead of violetlight V, green light G, and red light R. Furthermore, second rednarrow-band light NR2 of which the central wavelength or the peakwavelength is in the range of 630 to 670 nm as shown in FIG. 29 may beincluded in the second illumination light instead of blue light B, greenlight G, and red light R. In this case, it is preferable that specificlight amount conditions (the light amount condition of the first rednarrow-band light NR1 and the light amount condition of the second rednarrow-band light NR2) are determined so that the signal value of afirst red color signal (first specific color signal) for specificbiological tissue corresponding to at least specific biological tissueamong first image signals obtained in a case where the image of anobject to be observed is picked up using the first red narrow-band lightNR1 is equal to the signal value of a second red color signal (secondspecific color signal) for specific biological tissue corresponding toat least the specific biological tissue among second image signalsobtained in a case where the image of the object to be observed ispicked up using the second red narrow-band light NR2. Each of the firstred narrow-band light NR1 and the second red narrow-band light NR2 hassensitivity to the R-pixel of the image pickup sensor 48.

In the embodiment, the normal observation image processing unit 62, thefirst special observation image processing unit 63, and the secondspecial observation image processing unit 64 are provided and aprocessing unit to be used to perform processing is determined accordingto an observation mode by the signal switching unit 60 (see FIG. 2).However, processing may be performed by other methods. For example, aspecific image processing unit 90, which is a combination of theseprocessing units 62, 63, and 64, may be provided as shown in FIG. 30instead of the normal observation image processing unit 62, the firstspecial observation image processing unit 63, and the second specialobservation image processing unit 64; and image processing correspondingto each observation mode may be performed using a parametercorresponding to the observation mode.

For example, in the normal observation mode, the specific imageprocessing unit 90 sets a parameter to a parameter for a normal imageand performs image processing to generate a normal image. In the firstspecial observation mode, the specific image processing unit 90 sets aparameter to a parameter for a first special observation image andgenerates a first special observation image. In the second specialobservation mode, the specific image processing unit 90 sets a parameterto a parameter for a second special observation image and generates asecond special observation image. In the multi-observation mode, thespecific image processing unit 90 generates each of the first and secondspecial observation images by switching the parameter for a firstspecial observation image and the parameter for a second specialobservation image according to the switching of the first illuminationlight and the second illumination light.

Second Embodiment

In the first embodiment, the spectral reflectivity of already-knownspecific biological tissue is used to set specific light amountconditions that allow the signal value of a first blue color signal(first red color signal) for specific biological tissue and the signalvalue of a second blue color signal (second red color signal) forspecific biological tissue to be equal to each other. However, in asecond embodiment, image signals, which are obtained in a case where theimage of specific biological tissue is picked up during endoscopicdiagnosis using an endoscope 12, are used to calculate specific lightamount conditions.

In an endoscope system 100 according to the second embodiment, acalibration signal acquisition unit 102 and a light amountcondition-calculation unit 104 are provided in a processor device 16 asshown in FIG. 31. Further, a calibration mode used to calculate specificlight amount conditions during endoscopic diagnosis is provided in theendoscope system 100, and is switched by a mode changeover SW 13 a.Others of the endoscope system 100 are the same as those of theendoscope system 10 according to the first embodiment.

In a case where a user is to calculate specific light amount conditionsduring endoscopic diagnosis, the user operates the mode changeover SW 13a to switch a mode to the calibration mode in a case where a distal endpart 12 d of an endoscope reaches specific biological tissue as anobject for which specific light amount conditions are to be calculated.In a case where a mode is switched to the calibration mode, differentlight of the first illumination light and the second illumination lightand common light of the first illumination light and the secondillumination light are sequentially emitted to the specific biologicaltissue. Specifically, different light of the first illumination lightand the second illumination light are violet light V and blue light B,and common light of the first illumination light and the secondillumination light are green light G and red light R. Accordingly, thespecific biological tissue is illuminated with violet light V, bluelight B, green light G, and red light R sequentially. It is preferablethat the specific biological tissue is a part or all of biologicaltissue of any one of parts, such as the gullet, the stomach, and thelarge intestine. Further, it is preferable that the specific biologicaltissue includes at least one of, for example, superficial blood vesselsVS1, intermediate blood vessels VS2, or background mucous membrane BM.

In a case where the specific biological tissue is illuminated withviolet light V as shown in FIG. 32, the reflected light of violet lightV from the specific biological tissue is received by the image pickupsensor 48. In this case, image signals for violet light calibration(image signals for first calibration), which are obtained from imagepickup using violet light V, is output from the image pickup sensor 48.The image signals for violet light calibration are sent to the processordevice 16. The calibration signal acquisition unit 102 acquires theimage signals for violet light calibration from the endoscope 12.

In a case where the specific biological tissue is illuminated with bluelight B as shown in FIG. 33, the reflected light of blue light B fromthe specific biological tissue is received by the image pickup sensor48. In this case, image signals for blue light calibration (imagesignals for first calibration), which are obtained from image pickupusing blue light B, is output from the image pickup sensor 48. The imagesignals for blue light calibration are sent to the processor device 16.The calibration signal acquisition unit 102 acquires the image signalsfor blue light calibration from the endoscope 12.

In a case where the specific biological tissue is illuminated with greenlight G and red light R as shown in FIG. 34, the reflected light ofgreen light G and red light R from the specific biological tissue isreceived by the image pickup sensor 48. In this case, image signals forgreen/red light calibration (image signals for second calibration),which are obtained from image pickup using green light G and red lightR, are output from the image pickup sensor 48. The image signals forgreen/red light calibration are sent to the processor device 16. Thecalibration signal acquisition unit 102 acquires the image signals forgreen/red light calibration from the endoscope 12.

The light amount condition-calculation unit 104 calculates specificlight amount conditions of the first illumination light and the secondillumination light using the image signals for violet light calibration,the image signals for blue light calibration, and the image signals forgreen/red light calibration. For example, in a case where violet light Vof the first illumination light is emitted with light intensity α, bluelight B is emitted with light intensity β, and green light and red lightare emitted with light intensity γ, a blue color signal for violet lightcalibration (specific color signal for first calibration) output fromthe B-pixel of the image pickup sensor 48 among the image signals forviolet light calibration is denoted by αCV. Further, a blue color signalfor blue light calibration (specific color signal for first calibration)output from the B-pixel of the image pickup sensor 48 among the imagesignals for blue light calibration is denoted by βCB. Furthermore, ablue color signal for green/red light calibration (specific color signalfor second calibration) output from the B-pixel of the image pickupsensor 48 among the image signals for green/red light calibration isdenoted by γCGR.

A first blue color signal B1, which is output from the B-pixel of theimage pickup sensor 48 in a case where the first illumination light isemitted, is represented by Equation 3).

B1=αCV+γCGR  Equation 3)

Further, a second blue color signal B2, which is output from the B-pixelof the image pickup sensor 48 in a case where the second illuminationlight is emitted, is represented by Equation 4).

B2=βCB+γCGR  Equation 4)

Here, in a case where αCV is set to, for example, “100”, βCB is set to,for example, “50”, and γCGR is set to, for example, “20”, Equation 3) istransformed into Equation 3′).

B1=αCV/βCB×βCB+γCGR  Equation 3′)

Since αCV/βCB is “2”, Equation 3′) is as follows.

B1=2×βCB+γCGR  Equation 3′)

In order to make Equation 3′) and Equation 4) be equal to each other, itis necessary to multiply the first term of Equation 4) by “2”. From theabove description, the light amount condition-calculation unit 104 setsthe light intensity ratios Vs1:Bs1:Gs1:Rs1, which are the light amountcondition of the first illumination light, to “α:0: δ:ε”, sets the lightintensity ratios Vs2:Bs2:Gs2:Rs2, which are the light amount conditionof the second illumination light, to “0:2×β:δ:ε”, and calculatesspecific light amount conditions. “δ” denotes the light intensity ofgreen light G included in the first illumination light or the secondillumination light, and “ε” denotes the light intensity of red light Rincluded in the first illumination light or the second illuminationlight.

The hardware structures of the processing units included in theprocessor device 16 in the first and second embodiments, such as theimage acquisition unit 53, the lightness information calculation unit54, the DSP 56, the noise removing unit 58, the normal observation imageprocessing unit 62, the first special observation image processing unit63, the second special observation image processing unit 64, the staticimage storage unit 67, the display controller 66, the displayperiod-setting unit 66 a, the static image-storage controller 68, thespecific image processing unit 90, the calibration signal acquisitionunit 102, and the light amount condition-calculation unit 104, arevarious processors to be described below. The various processorsinclude: a central processing unit (CPU) that is a general-purposeprocessor functioning as various processing units by executing software(program); a programmable logic device (PLD) that is a processor ofwhich circuit configuration can be changed after manufacture, such as afield programmable gate array (FPGA); a graphical processing unit (GPU);a dedicated electrical circuit that is a processor having circuitconfiguration designed exclusively to perform various kinds ofprocessing; and the like.

One processing unit may be formed of one of these various processors, ormay be formed of a combination of two or more same kind or differentkinds of processors (for example, a plurality of FPGAs, a combination ofa CPU and an FPGA, or a combination of a CPU and a GPU). Further, aplurality of processing units may be formed of one processor. As anexample where a plurality of processing units are formed of oneprocessor, first, there is an aspect where one processor is formed of acombination of one or more CPUs and software as typified by a computer,such as a client or a server, and functions as a plurality of processingunits. Second, there is an aspect where a processor fulfilling thefunctions of the entire system, which includes a plurality of processingunits, by one integrated circuit (IC) chip as typified by System On Chip(SoC) or the like is used. In this way, various processing units areformed using one or more of the above-mentioned various processors ashardware structures.

In addition, the hardware structures of these various processors aremore specifically electrical circuitry where circuit elements, such assemiconductor elements, are combined.

The invention can be applied to various medical image processing devicesother than the processor device that is to be combined with theendoscope systems described in the first and second embodiments.

EXPLANATION OF REFERENCES

-   -   10: endoscope system    -   12: endoscope    -   12 a: insertion part    -   12 b: operation part    -   12 c: bendable part    -   12 d: distal end part    -   12 e: angle knob    -   13 b: static image-acquisition instruction unit    -   14: light source device    -   16: processor device    -   18: monitor    -   19: user interface    -   20: light source unit    -   20 a: violet light emitting diode (V-LED)    -   20 b: blue light emitting diode (B-LED)    -   20 c: green light emitting diode (G-LED)    -   20 d: red light emitting diode (R-LED)    -   21: light source controller    -   23: optical path-combination unit    -   24: light emission period-setting unit    -   26 a: slide bar    -   26 b: slide bar    -   27 a: slider    -   27 b: slider    -   30 a: illumination optical system    -   30 b: image pickup optical system    -   41: light guide    -   45: illumination lens    -   46: objective lens    -   48: image pickup sensor    -   48 b: B-filter    -   48 g: G-filter    -   48 r: R-filter    -   50: CDS/AGC circuit    -   53: image acquisition unit    -   54: lightness information calculation unit    -   56: digital signal processor (DSP)    -   58: noise removing unit    -   60: signal switching unit    -   62: normal observation image processing unit    -   63: first special observation image processing unit    -   64: second special observation image processing unit    -   66: display controller    -   66 a: display period-setting unit    -   67: static image storage unit    -   68: static image-storage controller    -   70: graph    -   71: graph    -   74: high-oxygen portion    -   76: high-oxygen portion    -   78: low-oxygen portion    -   80: low-oxygen portion    -   84 a: slide bar    -   84 b: slide bar    -   86 a: slider    -   86 b: slider    -   90: specific image processing unit    -   100: endoscope system    -   102: calibration signal acquisition unit    -   104: light amount condition-calculation unit    -   SP1: first special observation image    -   SP2: second special observation image    -   VP: violet light image    -   GRP: green-red light image    -   VS1: superficial blood vessel    -   VS2: intermediate blood vessel    -   BM: background mucous membrane

What is claimed is:
 1. An endoscope system comprising: a light sourcethat emits first illumination light and second illumination light havingan emission spectrum different from an emission spectrum of the firstillumination light; a light source controller that automaticallyswitches the first illumination light and the second illumination lightand emits each of the first illumination light and the secondillumination light for a light emission period of at least one or moreframes; an image pickup sensor that includes specific pixels havingsensitivity to the first illumination light and the second illuminationlight; and a processor configured to function as: an image acquisitionunit that acquires first image signals obtained in a case where an imageof biological tissue illuminated with the first illumination light ispicked up by the image pickup sensor, and second image signals obtainedin a case where an image of biological tissue illuminated with thesecond illumination light is picked up by the image pickup sensor; and adisplay controller that causes a display to automatically switch anddisplay a first observation image obtained on the basis of the firstimage signals and a second observation image obtained on the basis ofthe second image signals, wherein the first image signals include firstspecific color signals output from the specific pixels, and the secondimage signals include second specific color signals output from thespecific pixels, and the light source controller causes the firstillumination light and the second illumination light to be emitted underspecific light amount conditions, so that a signal value of the firstspecific color signal for specific biological tissue corresponding to atleast specific biological tissue, which is a part of the biologicaltissue, among the first specific color signals is equal to a signalvalue of the second specific color signal for specific biological tissuecorresponding to at least the specific biological tissue among thesecond specific color signals.
 2. The endoscope system according toclaim 1, wherein a light amount condition of the first illuminationlight and a light amount condition of the second illumination light in acase where a first calculation value obtained using a light intensity ofthe first illumination light, a spectral reflectivity of the specificbiological tissue, and a spectral sensitivity of the specific pixel isequal to a second calculation value obtained using a light intensity ofthe second illumination light, the spectral reflectivity of the specificbiological tissue, and the spectral sensitivity of the specific pixelare used as the specific light amount conditions.
 3. The endoscopesystem according to claim 2, wherein the spectral reflectivity of thespecific biological tissue is an average spectral reflectivity of aplurality of parts obtained by averaging of spectral reflectivities ofbiological tissue of the plurality of parts.
 4. The endoscope systemaccording to claim 3, wherein the plurality of parts include a gullet, astomach, and a large intestine.
 5. The endoscope system according toclaim 2, wherein the spectral reflectivity of the specific biologicaltissue is a spectral reflectivity of a background mucous membrane. 6.The endoscope system according to claim 2, wherein the spectralreflectivity of the specific biological tissue is an average spectralreflectivity of the entire biological tissue.
 7. The endoscope systemaccording to claim 2, wherein the spectral reflectivity of the specificbiological tissue is any one of a spectral reflectivity of a high-oxygenportion including a specific percentage or higher of oxyhemoglobin or aspectral reflectivity of a low-oxygen portion including a specificpercentage or higher of reduced hemoglobin.
 8. The endoscope systemaccording to claim 1, wherein the processor is further configured tofunction as: a calibration signal acquisition unit that acquires imagesignals for first calibration obtained in a case where an image of thespecific biological tissue illuminated with different light of the firstillumination light and the second illumination light is picked up by theimage pickup sensor and image signals for second calibration obtained ina case where an image of the specific biological tissue illuminated withcommon light of the first illumination light and the second illuminationlight is picked up by the image pickup sensor; and a light amountcondition-calculation unit that calculates the specific light amountconditions using a specific color signal for first calibration outputfrom the specific pixel among the image signals for first calibrationand a specific color signal for second calibration output from thespecific pixel among the image signals for second calibration.
 9. Anendoscope system comprising: a light source that emits firstillumination light and second illumination light having an emissionspectrum different from an emission spectrum of the first illuminationlight; a light source controller that automatically switches the firstillumination light and the second illumination light and emits each ofthe first illumination light and the second illumination light for alight emission period of at least one or more frames; an image pickupsensor that includes specific pixels having sensitivity to the firstillumination light and the second illumination light; and a processorconfigured to function as: an image acquisition unit that acquires firstimage signals obtained in a case where an image of biological tissueilluminated with the first illumination light is picked up by the imagepickup sensor, and second image signals obtained in a case where animage of biological tissue illuminated with the second illuminationlight is picked up by the image pickup sensor, wherein the firstillumination light includes violet light, green light, and red light andthe second illumination light includes blue light, green light, and redlight, the first image signals include first specific color signalsoutput from the specific pixels, and the second image signals includesecond specific color signals output from the specific pixels, and thelight source controller causes the first illumination light and thesecond illumination light to be emitted under specific light amountconditions, so that a signal value of the first specific color signalfor specific biological tissue corresponding to at least specificbiological tissue, which is a part of the biological tissue, among thefirst specific color signals is equal to a signal value of the secondspecific color signal for specific biological tissue corresponding to atleast the specific biological tissue among the second specific colorsignals.
 10. The endoscope system according to claim 9, wherein lightintensity ratios of the green light and the red light included in thefirst illumination light are equal to light intensity ratios of thegreen light and the red light included in the second illumination light,and the specific pixel is a blue pixel having sensitivity to the violetlight and the blue light.
 11. The endoscope system according to claim 9,wherein a light intensity ratio of the violet light included in thefirst illumination light is higher than a light intensity ratio of theblue light included in the first illumination light, a light intensityratio of the blue light included in the second illumination light ishigher than a light intensity ratio of the violet light included in thesecond illumination light, light intensity ratios of the green light andthe red light included in the first illumination light are equal tolight intensity ratios of the green light and the red light included inthe second illumination light, the light intensity ratio of the violetlight included in the first illumination light is different from thelight intensity ratio of the violet light included in the secondillumination light, and the light intensity ratio of the blue lightincluded in the first illumination light is different from the lightintensity ratio of the blue light included in the second illuminationlight, and the specific pixel is a blue pixel having sensitivity to theviolet light and the blue light.
 12. The endoscope system according toclaim 9, wherein the first illumination light includes first rednarrow-band light and the second illumination light includes second rednarrow-band light of which a wavelength is different from a wavelengthof the first red narrow-band light, and the specific pixel is a redpixel having sensitivity to the first red narrow-band light and thesecond red narrow-band light.
 13. The endoscope system according toclaim 9, wherein a light amount condition of the first illuminationlight and a light amount condition of the second illumination light in acase where a first calculation value obtained using a light intensity ofthe first illumination light, a spectral reflectivity of the specificbiological tissue, and a spectral sensitivity of the specific pixel isequal to a second calculation value obtained using a light intensity ofthe second illumination light, the spectral reflectivity of the specificbiological tissue, and the spectral sensitivity of the specific pixelare used as the specific light amount conditions.
 14. The endoscopesystem according to claim 13, wherein the spectral reflectivity of thespecific biological tissue is an average spectral reflectivity of aplurality of parts obtained by averaging of spectral reflectivities ofbiological tissue of the plurality of parts.
 15. The endoscope systemaccording to claim 14, wherein the plurality of parts include a gullet,a stomach, and a large intestine.
 16. The endoscope system according toclaim 13, wherein the spectral reflectivity of the specific biologicaltissue is a spectral reflectivity of a background mucous membrane. 17.The endoscope system according to claim 13, wherein the spectralreflectivity of the specific biological tissue is an average spectralreflectivity of the entire biological tissue.
 18. The endoscope systemaccording to claim 13, wherein the spectral reflectivity of the specificbiological tissue is any one of a spectral reflectivity of a high-oxygenportion including a specific percentage or higher of oxyhemoglobin or aspectral reflectivity of a low-oxygen portion including a specificpercentage or higher of reduced hemoglobin.
 19. The endoscope systemaccording to claim 9, wherein the processor is further configured tofunction as: a calibration signal acquisition unit that acquires imagesignals for first calibration obtained in a case where an image of thespecific biological tissue illuminated with different light of the firstillumination light and the second illumination light is picked up by theimage pickup sensor and image signals for second calibration obtained ina case where an image of the specific biological tissue illuminated withcommon light of the first illumination light and the second illuminationlight is picked up by the image pickup sensor; and a light amountcondition-calculation unit that calculates the specific light amountconditions using a specific color signal for first calibration outputfrom the specific pixel among the image signals for first calibrationand a specific color signal for second calibration output from thespecific pixel among the image signals for second calibration.